Packaging arrangements including a bottle or a like container, and an associated closure fitted thereto, are suitable for a wide variety of goods, in particular liquids such as beverages. In this regard, economical and effective closure constructions for containers including carbonated beverages, wherein the contents are pressurized, have proven challenging to perfect.
U.S. Pat. No. 4,378,893, to Wilde, et al., discloses a composite closure construction which has proven to be very commercially successful due to its high degree of suitability for use on containers having pressurized contents. This construction includes an internally threaded, outer plastic closure cap, with a sealing liner fitted in the closure cap adjacent to a top wall portion thereof. U.S. Pat. Nos. 4,343,754 and 4,497,765 disclose methods and apparatus for effecting efficient manufacture of this type of closure.
One particularly advantageous feature of this type of closure is the nature of its sealing arrangement. Specifically, the generally disc-shaped sealing liner of the closure includes an annular sealing bead portion which defines a generally inwardly facing sealing surface. By this arrangement, a so-called "top/side" seal is formed with the associated container, that is, sealing engagement is effected at both the upwardly facing top surface, and outwardly facing side surface of the container.
Experience has shown that the internal gas pressure of a container having a carbonated beverage or the like can act against the inside of the top wall of this type of closure, thereby acting to deform or bow the top wall upwardly. While this cold-flow phenomenon (sometimes referred to as "creep" of the plastic material) can lessen the sealing engagement of the closure with the top surface of the container, the combination top/side seal assures that the side seal is maintained, thus maintaining the sealing integrity of the construction.
Despite the desirable functional characteristics of this construction, certain conditions can detract from its effectiveness. One potential problem concerns the inevitable manufacturing tolerances encountered in container manufacture, wherein a closure may be fitted to either a relatively small or relatively large container. Similar containers made from different materials may also exhibit dimensional differences in their finishes.
The side seal of the closure is generated by compression of the liner material at the inside diameter of the annular sealing bead portion when the closure is applied to a bottle finish. The amount of liner compression is determined by the outside diameter of the bottle finish relative to the inside diameter of the sealing bead portion.
To form an effective seal, the relatively low compression of the liner material at the side seal by a smaller diameter bottle requires that the length (i.e., height) of the side seal be relatively long. In contrast, high compression of the liner material by a relatively large diameter bottle only requires a short side seal length to assure the desired sealing.
Accordingly, it is desirable to provide an arrangement which is configured to change the side seal length depending upon the finish diameter of the container to which the closure is fitted.
In addition to providing the desired degree of sealing engagement between the closure and the associated container, a closure should preferably be configured to facilitate high-speed, automatic application. As noted, a container having a relatively large outside diameter results in relatively high compression of the liner material attendant to closure application, and providing an arrangement which facilitates such application is desirable.
One undesirable result of the compression of the closure liner material can be an extrusion-like deformation of the material so that it tends to move past the annular retaining lip down the side wall of the bottle finish. This can have the undesirable effect of increasing the so-called vent release angle of the closure. Specifically, for threaded closures used on carbonated beverages, it is ordinarily desirable to facilitate the venting of gas pressure from within the container prior to release and disengagement of the closure threads. Under those conditions where the liner material has extruded past the retaining lip, the angle through which the closure must be rotated to release the seal, and thus initiate venting, can be undesirably increased, thereby decreasing the amount of rotation between initiation of venting and disengagement of the threads. Accordingly, it is desirable to minimize such extrusion of the liner material past the retaining lip.
Finally, it is generally desirable to enhance the efficiency of closure manufacture. As disclosed in the above-noted patents, closures of the subject type are formed by in situ compression molding of the liner material by depositing a pellet of molten plastic in the closure cap, and thereafter compressing and molding the molten material so that it flows against the annular liner retaining lip and forms the sealing liner.
To assure that the lining material is confined generally within the region defined by the annular lip, the use of an annular sleeve, which fits about the liner-shaping molding plunger, is preferred. This annular sleeve engages the annular lining retaining lip as the liner material is molded, thereby acting to confine the material as desired.
Problems can arise when attempting to line relatively hot and pliable closure caps. Experience has shown that under these conditions, the liner material can be forced past the relatively pliable retaining lip of the closure cap, resulting in plastic "flash" around the lip. This is undesirable because it can undesirably increase the vent release angle of the closure, and detracts from the aesthetic aspects of the construction.
With consideration of the above design problems, the present closure has been particularly configured to provide the desired degree of sealing for closures exhibiting varying diameters within normal tolerances, while at the same time providing consistent venting characteristics. High-speed manufacture and application are desirably accommodated.